System and method for measuring reflected optical distortion in contoured panels having specular surfaces

ABSTRACT

A system for measuring reflected optical distortion in a contoured panel having a specular surface includes a conveyor for conveying the panel in a first direction, at least one display projecting a preselected multi-phase non-repeating contrasting pattern, and at least one camera, each one of the cameras uniquely paired with one of the displays. The system may also include a control programmed to execute logic for controlling each of the cameras to acquire the desired images, and logic for analyzing and combining the data acquired by the cameras to construct a definition of the surface of the panel, and logic for performing one or more optical processing operations on the surface data to analyze the optical characteristics of the panel.

TECHNICAL FIELD

This invention relates to a method and apparatus for measuring reflectedoptical distortion in curved panels having specular surfaces.

BACKGROUND

Manufacturers of panels having specular surfaces, particularly panelsformed into various curved shapes, are interested in measuring andevaluating the amount of optical distortion in the formed panels thatmight be perceived by a human observer.

Various types of optical inspection systems are known. The opticalcharacteristics of a panel may be measured by acquiring and analyzingimage data corresponding to the image of a pre-defined, contrastingpattern that is reflected from one of the surfaces of the panel.

It is desirous to develop a system and method for quickly acquiring datacorresponding to the surface of a panel and analyzing the acquiredsurface data to assess and report on the optical characteristics of thepanel, particularly as the panel is being transported on a conveyorbetween or after other processing/fabricating operations.

SUMMARY

The disclosed system and method for measuring optical distortion in acontoured panel includes, as components, (1) a system and method foracquiring three-dimensional surface data corresponding to the panel, and(2) a system and method for receiving the acquired surface data andperforming one or more optical processing operations to analyze theoptical characteristics of the panel.

The surface data acquisition system may include a conveyor for conveyingthe panel in a first direction generally parallel to the first dimensionof the panel, at least one display projecting a preselected contrastingpattern, and at least one camera, each one of the cameras uniquelypaired with one of the displays, wherein each display and camera pairare mounted in a spaced-apart relationship a known distance and anglefrom the surface of the panel such that the camera detects the reflectedimage of the pattern projected on the surface of the panel from itsassociated display.

The surface data acquisition system may, in one embodiment, include twoor more cameras, each one of the cameras being uniquely paired with oneof the displays as described above, wherein each of the display andcamera pairs are spaced apart from each other at least in a seconddirection across the second dimension of the panel such that each cameradetects the reflected image of the pattern projected on the surface ofthe panel from only its associated display, and wherein the patternsdetected by the two or more cameras together cover the entire surface inthe direction of the second dimension of the panel.

The surface data acquisition system may also include a programmablecontrol including at least one processor programmed to execute logic forcontrolling each of the cameras to acquire at least one image of thereflected pattern of the associated display on the panel as the panel isconveyed across the path of the projected pattern in the firstdirection, and logic for analyzing and combining the data acquired bythe two or more cameras to construct surface data representative of thesurface of the panel.

The disclosed optical processing system may include at least oneprocessor including logic for receiving the captured image data andperforming one or more optical processing operations to analyze theoptical characteristics of the panel and display or otherwise reportselected information associated with the analysis.

The system for measuring optical distortion may utilize a singlecomputer which controls the conveyor and the operation of the cameras,and includes the previously described surface data acquisition logic, aswell as the optical distortion processing logic. Alternatively, theconveyor control, camera controls, surface data acquisition and opticalprocessing may be integrated but implemented on separate or multipleprocessors, in one or more programmable logic controllers and/orcomputers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic partial end view of one embodiment of thedisclosed panel optical inspection system;

FIG. 2 is a schematic top view of the disclosed panel optical inspectionsystem of FIG. 1;

FIG. 3 is a schematic view of a three-frequency pattern which may beemployed in one embodiment of the optical inspection system;

FIG. 4 is a schematic view of a two-frequency pattern which may beemployed in another embodiment of the optical inspection system;

FIG. 5 is a top diagrammatic view of the arrangement of multipledisplay/camera pairs shown in FIG. 2 including the angular orientationof the displays/cameras for a particular glass part;

FIG. 6 is a top view of a particular curved panel illustrating the areasof the panel surface analyzed by each of the display/camera pairsutilized in the system of FIG. 1;

FIG. 7 is a flow chart describing the logic employed in one embodimentof the disclosed optical inspection system;

FIG. 8 is a schematic illustration of the pertinent geometric parametersthat may be utilized to determine the elevation of a single point on thesurface of the panel according to the steps depicted in FIG. 9;

FIG. 9 is a flow chart describing the surface point resolution logicemployed in one embodiment of the surface data acquisition portion ofthe system;

FIG. 10 is a schematic diagram of one embodiment of the disclosedoptical inspection system installed in-line in a typical automotiveglass sheet forming and tempering line; and

FIG. 11 is a schematic diagram of another embodiment of the disclosedoptical inspection system installed in-line in a typical automotivewindshield forming line.

DETAILED DESCRIPTION

As required, detailed embodiments of the present invention are disclosedherein. However, it is to be understood that the disclosed embodimentsare merely exemplary of the invention that may be embodied in variousand alternative forms. The figures are not necessarily to scale; somefeatures may be exaggerated or minimized to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

Referring to FIG. 1, a panel optical inspection system, generallyindicated as 10, is disclosed and includes a conveyor 12 which conveysthe panel, which in the illustrated embodiment is a glass sheet, G, in afirst direction generally parallel to a first dimension of the panel. Inthe depicted embodiment, the contoured panel is a generally rectangularvehicle windshield or backlight, having a first dimension which is therelatively smaller dimension (and which may alternatively be referred toas the height) and a second, relatively larger dimension (which mayalternatively be referred to as the width). The panel is curved aboutone or more axes of curvature that are generally parallel to the firstdirection. The conveyor 12 may be a single conveyor dedicated solely totransporting the panel through the optical inspection system 10 whichmay be configured and/or operated as a stand-alone optical inspectionsystem. Alternatively, the conveyor 12 may be one of a series ofconveyors which convey the panel through a variety of processingstations, such as, for example with respect to glass sheets, heating,forming, and annealing or tempering stations found in a typicalautomotive, architectural and/or solar panel fabrication systems.

The optical inspection system 10 depicted in FIGS. 1 and 2 also includestwo or more displays 14-24. Each display projects a contrasting pattern,such as, for example, those patterns shown in FIGS. 4 and 5, whichpattern is projected onto the surface of the panel as it is conveyedbeneath the screens. The system 10 also includes two or more cameras28-40. Each one of the cameras 28-40 is uniquely paired with one of eachof the corresponding number of displays 14-26. In the depictedembodiment of the system 10, an aperture is formed in the center of eachof the displays 14-26. The camera associated with a particular displayis mounted such that the viewing aperture of the camera extends throughthe aperture in its associated display such that the principal viewingaccess of the camera is perpendicular to the surface the screen. Itwill, of course, be appreciated by those skilled in the art that eachcamera may be alternatively arranged at other locations with respect toits associated display, so long as the camera is positioned to detectthe reflected image of the pattern projected on the surface of the panelfrom that display, and not detect reflected images of patterns projectedfrom other displays in its field of view.

Referring still to FIGS. 1 and 2, the number and placement of thedisplays is dependent upon the size of the displays, as well as thewidth and the curvature of the panel. In the depicted embodiment of thesystem 10, the camera/display pairs are positioned such that theprincipal viewing axis of each camera is generally perpendicular to thesurface of the panel. The total number of camera/display pairs must besufficient such that the total number of projected patterns span theentire width of the surface of the panel part to be analyzed.

Referring again to FIG. 1, the optical inspection system 10 alsoincludes a programmable control, depicted in this embodiment as acomputer 42, which includes at least one processor programmed to detectthe panel as it advances on the conveyor, control each of the cameras28-40 to acquire one or more images of the pattern reflected off thesurface of the panel as it is conveyed below the cameras/displays,construct the definition of the panel surface, and perform the desiredoptical distortion analysis (using, for example, the techniques depictedand described in FIGS. 7-9, and as further described hereinafter). Inany embodiments of the system 10 (such as the embodiment depicted in theFigures) where the field of view of a camera in any width zone issmaller than the first dimension (height) of the panel, the systemcontrol may be programmed to acquire multiple images as the glass isconveyed in the first direction. It will be appreciated that the numberof images acquire by each camera should be sufficient that the surfaceinformation developed from each image (as hereinafter described) can becombined to form a description of the entire surface across the height(i.e., in the direction of conveyance) of the panel.

Where, as in the depicted embodiment, the cameras are mounted with theirviewing aperture extending through an aperture in the display, thesystem control 42 may be programmed to acquire multiple images as thepanel is conveyed in the first direction to insure that an image of thereflected pattern is obtained in a previous or subsequent image of themoving panel for that portion of the surface of the panel that, in anyone of the captured images, is in the area of reflection of the displayaperture. Again, it will be appreciated that the number of imagesacquire by each camera should also be sufficient that the surfaceinformation developed from each image (as hereinafter described) can becombined to form a description of the entire surface across the heightin the area in which a single image might include an image of thedisplay aperture rather than the reflected pattern.

The surface descriptions for each of the cameras are similarly combinedto form a description of the entire surface across the width (or acrossthe area of interest in the direction of the width) of the panel.

Referring to FIG. 3, in one embodiment the screen pattern is athree-frequency pattern constructed by superimposition of threedifferent frequency sinusoidal patterns in each of the x and ydirections of the coordinate system employed by the system logic. Itshould be noted that, in the illustrated embodiment, the x-y coordinatesystem axes are chosen to be oriented such that they are coincident withthe x and y axes of the display (and, as well, the y axis is parallel tothe direction of travel of the conveyor and the x axis is orthogonal tothe direction of travel of the conveyor).

The sinusoidal patterns are chosen and combined to insure that theportion of the resultant pattern appearing on the display isnon-repetitive, thereby ensuring that, for the image data collected,each pixel in the camera's field of view will correspond uniquely to asingle point on the display. Each of the three frequencies may berelatively prime values, and are selected such that they are spacedapart within the envelope of frequencies bound by the minimum andmaximum frequency limits of the camera's optics.

The image of this three-frequency pattern reflected from the surface ofthe panel may then be mathematically deconstructed into three singlefrequency images in each of the x and y direction. Phase informationcorresponding to each of the three frequencies can then be isolated andutilized as hereinafter described to develop an accurate description ofthe panel surface.

In another embodiment, illustrated in FIG. 4, a two-frequency patternmay be utilized. This two-frequency pattern may be constructed bysuperimposition of two different frequency sinusoidal patterns in eachof two orthogonal directions which are rotated (or skewed) about theaxes that are used to separate the analysis into orthogonal components,such that each of the sinusoidal components of the pattern yields phaseinformation in both the x and y directions. In the illustratedembodiment, the x, y coordinate system axes that are used by the systemlogic to separate the analysis into orthogonal components are coincidentwith the x and y axes of the display (and the y axis is as well,coincident with the direction of conveyance).

Thus, in the illustrated embodiment, the orthogonal directions of thesinusoidal patterns are skewed from the x and y axes of the display. Itwill be appreciated, however, that any other convenient orientation maybe chosen for the axes that are used by the system to separate theanalysis into orthogonal components, so long as the sinusoidal patternsare rotated about the axes that are used to separate the analysis intoorthogonal components to yield phase information in both the x and ydirections.

Again, the sinusoidal patterns are chosen (relatively prime frequenciesand spaced apart as described above) and combined to insure that theportion of the resultant pattern appearing on the display isnon-repetitive, thereby ensuring that the image data collected that eachpixel in the camera's field of view will correspond uniquely to a singlepoint on the display.

The image of this two-frequency pattern reflected from the surface ofthe panel may then be similarly mathematically deconstructed. Again,phase information corresponding to each of the two frequencies can beisolated and utilized as hereinafter described to develop an accuratedescription of the panel surface.

It will be appreciated by those skilled in the art that, by employing amulti-frequency, non-repeating pattern and employing the deflectometrytechniques hereinafter described, an accurate mathematical descriptionof the panel surface may be obtained from a single image for each pointon the surface of the panel from which the camera detects the reflectedpattern. It is thus unnecessary to capture utilize multiple patterns,and/or multiple images, except as described herein where multiple imagesare acquired as the panel is moved on the conveyor to construct asurface for that portion of the panel that does not reflect theprojected pattern in any single acquired image (e.g., (1) that portionof the panel directly below the aperture in the screen, or (2) for thatportion of the panel that is not in the viewing area of the camera dueto the fact that the height of the panel is greater that the projectedpattern from the screen in the direction of conveyance).

Referring now to FIGS. 5 and 6, in the illustrated embodiment, and forthe depicted panel, glass sheet part G, the second dimension (width) ofthe panel was divided into seven zones. These zones were identified asrequired due to the dimension of display pattern viewed by the camera,and the width dimension and curvature of the particular panel part. Inthis example, first zone display 20 is oriented at an angle of about 25°counterclockwise from horizontal (when viewed as in FIG. 1), display 18is angled at about 15° counterclockwise, display 16 is angled at about7.5° counterclockwise, display 14 is approximately horizontal, display22 is angled at approximately 7.5° clockwise from horizontal, display 24is angled at about 15° clockwise, and display 26 is angled at about 25°clockwise. In the illustrated embodiment, the seven displays 14-26 arearranged in in the direction of conveyance of the panel G. However, aswill be appreciated by those skilled in the art, other arrangements maybe optimal for panel parts of different widths and curvatures, providedthat the screens are arranged such that each associated camera detectsonly the reflected pattern from its associated display in its field ofview, and the surface areas detected by all cameras together comprisethe surface across the entire width of the panel part.

The panel optical inspection system 10 includes a surface dataacquisition system which employs the above-described camera and displaypairs and acquired images, as well as logic for developing an accuratethree-dimensional description of the surface from the reflected patternsfrom each image, and logic for combining the surface descriptionsdeveloped from the images as hereinafter described to obtain an accuratemathematical description of the entire surface of the panel.

The panel optical inspection system 10 may also, in addition to thesurface data acquisition system, include one or more computers and/orprogrammable controls including logic for processing the acquiredsurface data to analyze the optical characteristics of the panel.

The optical inspection system 10 may, in turn, be incorporated into asystem for fabricating panels including one or more processing stationsand one or more conveyors for conveying the panels from station tostation during processing, such as fabrication systems 200 and 300schematically shown in FIGS. 10 and 11.

FIG. 7 describes the method 80 performed by the control logic of thedisclosed optical inspection system 10. When the system 10 determinesthat a panel is in the appropriate position on the conveyor, the systemactivates the appropriate camera(s), at 82, to acquire an image of thepattern reflected from the surface of the panel. The position of thepanels can be determined using conventional sensors.

As indicated at 84, one or more additional images may be obtained fromeach camera, as required, as the panel moves on the conveyor. Aspreviously described, the number of images acquired by each camera isdetermined by at least two considerations. First, in embodiments of thesystem wherein the cameras are mounted within an aperture of theirassociated displays, a sufficient number of images must be acquired toensure that the system acquires a reflected image of the pattern for allof the points in the viewing area, including those points from which thedisplay pattern is not reflected in a particular image due to the factthat it is located within the area that includes a reflection of theaperture. Second, multiple images may be required as the panel isconveyed across the viewing area of the camera in embodiments of thesystem where the field of view of the camera is not large enough toacquire a reflection of the display pattern from the surface of thepanel across its entire first dimension (i.e., the entire height) in oneimage.

For each of the acquired images, the system, at 86, must determine theprecise location in three-space of each point on the surface of thepanel based upon the reflected pattern in the image. As previouslydescribed, the use of a pattern which is non-repeating in the camera'sviewing area ensures that each point on the display screen that isreflected within the viewing area of the camera will be uniquelyassociated with a pixel that detects the reflected pattern. Conventionalimage processing techniques may be employed to determine the x and ylocations (i.e., in the focal plane of the camera) for each point on thesurface of the panel that is in the viewing area of the camera for thatimage. Other known processing techniques may be employed to determinethe z location (a.k.a. the elevation) of each point. In the disclosedembodiment, a mapping vector technique is employed (as depicted in FIGS.8 and 9, and as more fully described hereinafter) to determine theelevation of each single point on the surface of the panel from theimage of the reflected projected pattern.

In one embodiment, the x, y, and z values developed for each point inthe viewing area of a particular camera are typically developed in acoordinate system associated with that camera. In one embodiment, forexample, the origin of the coordinate system for each camera is set atthat camera's origin 98 (as shown in FIG. 8). The resulting collectionof points associated with the surface in the viewing area of each camera(“the point cloud”) may then be combined for each image collected bythat camera.

The system, at 88, then combines the developed surface data for each ofthe images acquired from all of the cameras to obtain the surfacedefinition which identifies the location of each point in three-spacefor the entire surface of the panel. In one embodiment, the point cloudsfor each camera are converted to a common (“global”) coordinate system,and the point clouds are then combined to form the entire surface.

It will be appreciated that one or more other coordinate systems/originsmay be selected and employed based upon a particular system'scamera/display architecture and/or for computational convenience.Similarly, the combination of the surface developed from the individualacquired images may be performed using other conventional image dataprocessing techniques.

The system then, at 90, performs one or more known optical processingtechniques to determine any desired indicia of the reflective optics ofthe surface. For example, in one embodiment, the system 10 may besuitably programmed to analyze the developed surface to determine (1)various desired indicia of optical distortion, including themagnification and lens power, for selected portions, or for theentirety, of the surface of each panel as it is transported through thesystem.

FIGS. 8 and 9 illustrate, respectively, the theoretical basis and themethod performed by the control logic for determining the elevation (zvalue) of each point on the surface of the panel from the image of thereflected projected pattern for each acquired image. FIG. 8 illustratesthe pertinent geometrical relationships between the camera 28, thedisplay screen 14, and the surface of the panel (which is depicted inFIG. 8 as a glass sheet, G). The three principles used to determine theelevation of a single point on the surface of the panel from a reflectedprojected image are (1) the surface of any object can be defined by thenormal vector 92 for each discrete point of the surface; (2) the law ofreflection defines the normal vector 92 at each point by bisecting theangle between the incident ray 94 and the reflected ray 96 of light(also referred to herein as the “geometric optical” or “reflectionangle” equation); and (3) the normal vector can also be defined by thedifferential geometry which describes each point on the surface of thepanel (also referred to herein as the “differential geometry” equation).

Referring still to FIG. 8, based upon the law of reflection, theincident ray is defined entirely by the camera intrinsics. Thus eachpixel in the cameras receptor cell at the cameras origin 98 sees a pointin space at varying distances through the lens. Continuing with the lawof reflection, the reflected ray 96 is defined by a screen position anda surface point on the panel. The distance is constrained only where itintersects the incident ray 94. There are two mathematical expressionswhich define the normal vector 92. One is derived from the law ofreflection. The second differential equation is derived from thegeometric partial differentiation at any point on the surface. To solvethe corresponding differential equations, a mapping vector 100 needs tobe established, which defines, for each pixel, where the reflected raywill hit the projected pattern on the display (viewed from the cameraorigin). Once the mapping field (i.e., the set of mapping vectors foreach pixel in the camera's field of view) is established, the distancesfrom the camera's origin and each discrete point on the surface can becalculated.

The geometric optical equation is:

$\overset{\rightharpoonup}{n} = \left. ||\overset{\rightharpoonup}{v}||{\left( {\overset{\rightharpoonup}{m} - {s\frac{\overset{\rightharpoonup}{v}}{\left| \overset{\rightharpoonup}{v} \right|}}} \right) -}||{\overset{\rightharpoonup}{m} - {s\frac{\overset{\rightharpoonup}{v}}{\left| \overset{\rightharpoonup}{v} \right|}}}||\left( \overset{\rightharpoonup}{v} \right) \right.$

Where n is the surface normal, v is the camera pixel vector, m is themapping vector, and s is the distance from the camera to the surface(along the camera vector so that the surface point

$\left( {p = {s\frac{v}{|v|}}} \right).$

The differential geometry describes the points on the surface of theglass sheet:

$\overset{\rightharpoonup}{n} = {\frac{\partial\overset{\rightharpoonup}{p}}{\partial x} \times \frac{\partial\overset{\rightharpoonup}{p}}{\partial y}}$

Since n is the cross product of the two differentials, it is bydefinition orthogonal to both, yielding:

${\overset{\rightharpoonup}{n} \cdot \frac{\partial\overset{\rightharpoonup}{p}}{\partial x}} = {{\overset{\rightharpoonup}{n} \cdot \frac{\partial\overset{\rightharpoonup}{p}}{\partial y}} = 0}$

Solving these for the elevation, s:

${\left( \left. ||\overset{\rightharpoonup}{v}||{\left( {\overset{\rightharpoonup}{m} - {s\frac{\overset{\rightharpoonup}{v}}{\left| \overset{\rightharpoonup}{v} \right|}}} \right) -}||{\overset{\rightharpoonup}{m} - {s\frac{\overset{\rightharpoonup}{v}}{\left| \overset{\rightharpoonup}{v} \right|}}}||\left( \overset{\rightharpoonup}{v} \right) \right. \right) \cdot \frac{\partial\overset{\rightharpoonup}{p}}{\partial x}} = 0$${\left( \left. ||\overset{\rightharpoonup}{v}||{\left( {\overset{\rightharpoonup}{m} - {s\frac{\overset{\rightharpoonup}{v}}{\left| \overset{\rightharpoonup}{v} \right|}}} \right) -}||{\overset{\rightharpoonup}{m} - {s\frac{\overset{\rightharpoonup}{v}}{\left| \overset{\rightharpoonup}{v} \right|}}}||\left( \overset{\rightharpoonup}{v} \right) \right. \right) \cdot \frac{\partial\overset{\rightharpoonup}{p}}{\partial y}} = 0$

FIG. 9 illustrates how a suitably programmed computer could implementthis mapping vector technique 102. At 104 the system develops a mappingvector that defines where the reflected ray projects to the display(again, viewed mathematically from the camera origin). A firstexpression, the geometric optical equation, at 106, defines the surfacenormal vector for each point on the panel surface within the camera'sviewing area based upon the law of reflection. A second equation, thedifferential geometry equation, at 108, defines the surface normalvector-based on the multiplication of the partial differentials whichdescribe the point on the surface in the x, y directions. These twoequations may be solved simultaneously using the mapping vector toobtain the elevation, s (that is, the z distance-the distance betweenthe panel surface and the camera origin) for each point on the panelsurface that is within the viewing area of the camera. This information,coupled with the previously developed x and y locations of each surfacepoint, yields a specific description, in x, y, and z, for each point onthe surface.

It will be appreciated by those skilled in the art that other knownmethods may be utilized to develop unambiguous locations in threedimensions for each of the points on the surface of the panel based uponthe unambiguous x and y locations of the reflected patterns at eachpixel location of the image, and the geometrical relationship betweenthe focal plane of the camera, the display screen, and the panel.However, it has been determined that the elevation of each point on thesurface of the panel can be quickly determined using the principlesdescribed above and illustrated in FIG. 8, and the technique describedabove and illustrated in FIG. 9, without resorting to projectingmultiple, varying patterns and/or analyzing multiple images of the sameviewing area to thereby determine a three-dimensional definition of thepanel surface.

Referring again to FIGS. 1 and 2, the disclosed panel optical inspectionsystem 10 may be mounted in-line to inspect panels as they aretransported on a conveyor associated with a panel processing systemwhich performs multiple fabricating operations on the panels. Thedisclosed system 10 includes a surface data acquisition system and acomputer including logic for receiving the captured image data,developing a three-dimension description of the panel surface from theimage data, performing one or more optical processing operations toanalyze the optical characteristics of the panel and displaying orotherwise reporting selected information associated with the opticalanalysis. As previously described, computer 42 may be operably connectedto the conveyor and cameras to perform the image acquisition, thesurface development, and the optical processing described herein.Alternatively, computer 42 may be combined with one or more othercomputers and/or programmable controls to perform these functions.

The system 10 may also be programmed by the user to graphically andnumerically display various indicia of optical distortion, includingthose indicia most relevant to industry standards, or other indiciaconsidered relevant in the industry to the analysis of the opticalreflection quality of formed and fabricated panels.

The digital cameras 28-40 are each connected via a conventional dataline to one or more computers, such as computer 42, which may besuitably programmed to acquire the digital image data from the camera,process the image data to obtain the desired surface definition for thepanel, and analyze the data to develop various indicia of distortion.The computer 42 may also be programmed to present the derived imagedistortion information in both graphical (e.g., color-coded images) andstatistical forms. If desired, various other statistical data can bederived and reported for predefined areas of the panel, including themaximum, minimum, range, mean, and standard deviation in lens power, orother indices of distortion which may be of interest.

As will be appreciated by those skilled in the art, the opticalinspection system 10 may additionally or alternatively employ otherknown image processing techniques to collect and analyze the acquiredimage data, develop a definition of the surface, and provide variousindicia of the reflected optical characteristics for each panel.

In one embodiment, the displays 14-26 are light boxes that utilizeconventional lighting (such as fluorescent lights) behind a translucentpanel upon which the contrasting pattern is printed, painted, orotherwise applied using conventional methods. The digital cameras 28-40are connected to the computer 60 using known methods, preferably so thatthe acquisition of the image by the camera may be controlled by thecomputer 42.

FIG. 11 illustrates a typical glass sheet heating, bending, andtempering system 200 which includes the in-line optical inspectionsystem 10, as well as the surface data acquisition system, of thepresent invention. In this installation, the glass sheets (indicated asG) enter a heating zone 202 where the glass is softened to a temperaturesuitable for forming the glass into the desired shape. The heated glasssheet is then conveyed to a bending station 204 where the softened sheetis formed to the desired shape, and thereafter further conveyed to acooling station 206 where the glass sheet is cooled in a controlledmanner to achieve the appropriate physical characteristics. In thisembodiment, the panel would then be conveyed out of the cooling stationonto a conveyor from which the glass sheet is conveyed for imageacquisition and analysis by the disclosed optical inspection system 10.Following the measurement, the glass sheet would be moved on theconveyor 12 for further processing. It will be appreciated that thetransport and conveyance of the glass can be achieved by using knowntechniques such as by roller, air-float, or belt conveyors, positioners,and robotic arms, in order to handle the glass in the manner described.It will also be appreciated that a plurality of conveyors, each of whichmay be independently controlled to move the glass sheets through thedifferent processing stations at speeds to efficiently govern the flowand processing of the glass sheets throughout the system 200.

FIG. 12 similarly schematically illustrates an in-line opticalinspection system 10 and the associated surface data acquisition systemof the present invention in a typical automotive windshield fabricationsystem 300, which may include a heating station 302, a bending station304, a cooling station 306, and a lamination station 308, upstream ofthe optical inspection system 10.

Selected data output by the disclosed in-line optical inspection system10 may also be provided as input to the control logic for the associatedglass sheet heating, bending, and tempering system 200 (or automotivewindshield fabrication system 300, or other panel fabrication/processingsystem) to allow the control(s) associated with one or more of thestations the system to modify its (their) operating parameters as afunction of the optical data developed from previously processed glasssheets (or panels).

It will be appreciated that the optical inspection system 10 of thepresent invention could alternatively be mounted in-line at variousother points in the above-described and other panel fabrication systemsas desired to maximize the production rate of the system, so long as theoptical distortion measurements are taken after the panel has beenformed to its final shape.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms of the invention. Rather,the words used in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the invention.Additionally, the features of various implementing embodiments may becombined to form further embodiments of the invention.

What is claimed is:
 1. A system for measuring the opticalcharacteristics of a curved panel having a specular surface, the panelhaving a first dimension and a second dimension, wherein the panel iscurved at least about one or more axes of curvature which are generallyparallel to the first dimension, the apparatus comprising: a conveyorfor conveying the panel in a first direction generally parallel to thefirst dimension of the panel; at least two displays, each displayprojecting a preselected contrasting pattern, at least two cameras, eachone of the at least two cameras being uniquely paired with one of thedisplays, wherein each display and camera pair are mounted in aspaced-apart relationship a known distance and angle from the surface ofthe panel such that the camera detects the reflected image of thepattern projected on the surface of the panel from its associateddisplay, and wherein each of the display and camera pairs are spacedapart from each other at least in a second direction across the seconddimension of the panel such that each camera detects the reflected imageof the pattern projected on the surface of the panel from only itsassociated display, and wherein the patterns detected by the camerastogether cover the entire surface in the direction of the seconddimension of the panel; and a programmable control including at leastone processor programmed to execute logic for controlling each of thecameras to acquire at least one image of the reflected pattern of theassociated display on the panel as the panel is conveyed across the pathof the projected pattern in the first direction, logic for analyzing andcombining the data acquired by the cameras to construct surface datarepresentative of the surface of the panel, and logic for analyzing thedata representative of the surface of the panel to determine opticalcharacteristics of the panel.
 2. The system of claim 1 wherein the firstdimension is the minor dimension of the panel and the second dimensionis the major dimension of the panel.
 3. The system of claim 1 whereinthe logic for analyzing and combining the data acquired by the camerasto construct surface data representative of the surface of the panelincludes logic for constructing surface data representative of theentire surface across the second dimension of the panel.
 4. The systemof claim 1 wherein a single image of the reflected patterns projected bythe displays from each of the associated cameras cannot be combined todefine data representative of the surface of the panel across the entiresecond dimension of the panel, and wherein the programmable controlincludes at least one processor programmed to execute logic forcontrolling each of the cameras to acquire multiple images of thereflected pattern of the associated display on the panel as the panel isconveyed across the path of the projected pattern in the firstdirection, and logic for analyzing and combining the data acquired bythe multiple images acquired by each camera to construct surface datarepresentative of the surface of the panel across the entire firstdimension of the panel.
 5. The system of claim 1 wherein each displayincludes an aperture, and wherein the associated camera is mountedbehind its associated display such that the principal axis of the camerais generally normal to the surface of the display and the image isreceived by the camera through the aperture, and wherein theprogrammable control includes logic for controlling each of the camerasto acquire multiple images of the reflected pattern of the associateddisplay on the panel as the panel is conveyed in the first direction forat least a distance greater than the size of the aperture, and logic foranalyzing and combining the data from the multiple images to define datarepresentative of the surface of the panel in the area for which any oneof the acquired images includes a reflected image of the aperture. 6.The system of claim 1 wherein the logic for analyzing and combining thedata acquired by the cameras to construct surface data representative ofthe surface of the panel includes at least: logic for developing, foreach pixel in in the viewing area of the camera for each acquired image,a mapping vector that defines where the reflected ray projects from thecamera origin to the associated display; and logic for developing, foreach pixel in the viewing area of the camera for each acquired image,the elevation value, s, of the point, by simultaneously solving (1) thegeometric optical equation and (2) the differential geometry equation,using the mapping vector.
 7. The system of claim 1 wherein thepreselected contrasting pattern is non-repeating over the entire viewingarea of the camera.
 8. The system of claim 8 wherein the preselectedcontrasting pattern is a three-frequency pattern, constructed bysuperimposition of three different frequency sinusoidal patterns in eachof the x and y directions of the coordinate system employed by thesystem logic.
 9. The system of claim 8 wherein the preselectedcontrasting pattern is a two-frequency pattern, constructed bysuperimposition of two different frequency sinusoidal patterns in eachof the x and y directions of the pattern, where the two differentfrequency sinusoidal patterns are rotated with respect to the axes ofthe coordinate system employed by the system logic.
 10. The system ofclaim 1 wherein the logic for analyzing the data representative of thesurface of the panel to determine optical characteristics of the panelincludes logic for determining selected indicia of optical distortionassociated with each point of interest on the surface of the panel. 11.The system of claim 10 wherein the selected indicia of distortionincludes lens power.
 12. The system of claim 1 wherein the system isincorporated into a system for fabricating curved panels includingmultiple processing stations and one or more conveyors for conveying thepanel from station to station during processing.
 13. A system forfabricating curved panels having specular surfaces including one or moreprocessing stations and one or more conveyors for conveying the panelfrom station to station during processing, one of the processingstations including an apparatus for measuring the opticalcharacteristics of a panel as the panel is conveyed in a first directiongenerally parallel to the first dimension of the panel, the apparatuscomprising; at least two displays, each display projecting a preselectedcontrasting pattern, at least two cameras, each one of the cameras beinguniquely paired with one of the displays, wherein each display andcamera pair are mounted in a spaced-apart relationship a known distanceand angle from the surface of the panel such that the camera detects thereflected image of the pattern projected on the surface of the panelfrom its associated display, and wherein each of the display and camerapairs are spaced apart from each other at least in a second directionacross the second dimension of the panel such that each camera detectsthe reflected image of the pattern projected on the surface of the panelfrom only its associated display, and wherein the patterns detected bythe cameras together cover the entire surface in the direction of thesecond dimension of the panel; and a programmable control including atleast one processor programmed to execute logic for controlling each ofthe cameras to acquire at least one image of the reflected pattern ofthe associated display on the panel as the panel is conveyed across thepath of the projected pattern in the first direction, logic foranalyzing and combining the data acquired by the cameras to constructsurface data representative of the surface of the panel, and logic foranalyzing the data representative of the surface of the panel todetermine optical characteristics of the panel.
 14. The system of claim13 wherein the first dimension is the minor dimension of the panel andthe second dimension is the major dimension of the panel.
 15. The systemof claim 13 wherein the logic for analyzing and combining the dataacquired by the cameras to construct surface data representative of thesurface of the panel includes logic for constructing surface datarepresentative of the entire surface across the second dimension of thepanel.
 16. The system of claim 13 wherein a single image of thereflected patterns projected by the displays from each of the associatedcameras cannot be combined to define data representative of the surfaceof the panel across the entire second dimension of the panel, andwherein the programmable control includes at least one processorprogrammed to execute logic for controlling each of the cameras toacquire multiple images of the reflected pattern of the associateddisplay on the panel as the panel is conveyed across the path of theprojected pattern in the first direction, and logic for analyzing andcombining the data acquired by the multiple images acquired by eachcamera to construct surface data representative of the surface of thepanel across the entire first dimension of the panel.
 17. The system ofclaim 13 wherein each display includes an aperture, and wherein theassociated camera is mounted behind its associated display such that theprincipal axis of the camera is generally normal to the surface of thedisplay and the image is received by the camera through the aperture,and wherein the programmable control includes logic for controlling eachof the cameras to acquire multiple images of the reflected pattern ofthe associated display on the panel as the panel is conveyed in thefirst direction for at least a distance greater than the size of theaperture, and logic for analyzing and combining the data from themultiple images to define data representative of the surface of thepanel in the area for which any one of the acquired images includes areflected image of the aperture.
 18. The system of claim 13 wherein thelogic for analyzing and combining the data acquired by the cameras toconstruct surface data representative of the surface of the panelincludes at least: logic for developing, for each pixel in in theviewing area of the camera for each acquired image, a mapping vectorthat defines where the reflected ray projects from the camera origin tothe associated display; and logic for developing, for each pixel in theviewing area of the camera for each acquired image, the elevation value,s, of the point, by simultaneously solving (1) the geometric opticalequation and (2) the differential geometry equation, using the mappingvector.
 19. The system of claim 13 wherein the logic for analyzing thedata representative of the surface of the panel to determine opticalcharacteristics of the panel includes logic for determining selectedindicia of optical distortion associated with each point of interest onthe surface of the panel.
 20. The system of claim 19 wherein theselected indicia of distortion includes lens power.
 21. A system formeasuring the optical characteristics of a curved panel having aspecular surface, the panel having a first dimension and a seconddimension, wherein the panel is curved at least about one or more axesof curvature which are generally parallel to the first dimension, theapparatus comprising: a conveyor for conveying the panel in a firstdirection generally parallel to the first dimension of the panel; adisplay projecting a preselected contrasting pattern on the surface ofthe panel, a camera mounted in a spaced-apart relationship a knowndistance and angle from the surface of the panel such that the cameradetects the reflected image of the pattern projected on the surface ofthe panel from the display, and wherein the pattern detected by thecamera covers the entire portion of interest on the surface in thedirection of the second dimension of the panel; and a programmablecontrol including at least one processor programmed to execute logic forcontrolling each of the camera to acquire at least one image of thereflected pattern of the associated display on the panel as the panel isconveyed across the path of the projected pattern in the firstdirection, logic for analyzing and combining the data acquired by thecamera to construct surface data representative of the surface of thepanel, and logic for analyzing the data representative of the surface ofthe panel to determine optical characteristics of the panel; and whereinthe logic for analyzing and combining the data acquired by the camera toconstruct surface data representative of the surface of the panelincludes at least: logic for developing, for each pixel in in theviewing area of the camera for each acquired image, a mapping vectorthat defines where the reflected ray projects from the camera origin tothe associated display; and logic for developing, for each pixel in theviewing area of the camera for each acquired image, the elevation value,s, of the point, by simultaneously solving (1) the geometric opticalequation and (2) the differential geometry equation, using the mappingvector.
 22. A method for measuring the optical characteristics of acurved panel having a specular surface, the panel having a firstdimension and a second dimension, wherein the panel is curved at leastabout one or more axes of curvature which are generally parallel to thefirst dimension, the method including at least the steps of: conveyingthe panel in a first direction generally parallel to the first dimensionof the panel; projecting a preselected contrasting pattern from each ofat least two displays onto the surface of the panel providing at leasttwo cameras, each one of the cameras being uniquely paired with one ofthe displays, wherein each display and camera pair are mounted in aspaced-apart relationship a known distance and angle from the surface ofthe panel for detecting the reflected image of the pattern projected onthe surface of the panel from its associated display, and wherein eachof the display and camera pairs are spaced apart from each other atleast in a second direction across the second dimension of the panelsuch that each camera detects the reflected image of the patternprojected on the surface of the panel from only its associated display,and wherein the patterns detected by the cameras together cover theentire surface in the direction of the second dimension of the panel;and controlling each of the cameras to acquire at least one image of thereflected pattern of the associated display on the panel as the panel isconveyed across the path of the projected pattern in the firstdirection; analyzing and combining the data acquired by the cameras toconstruct surface data representative of the surface of the panel; andanalyzing the data representative of the surface of the panel todetermine optical characteristics of the panel.
 23. A method formeasuring the optical characteristics of a curved panel having aspecular surface, the panel having a first dimension and a seconddimension, wherein the panel is curved at least about one or more axesof curvature which are generally parallel to the first dimension, themethod including at least the steps of: conveying the panel in a firstdirection generally parallel to the first dimension of the panel;projecting a preselected contrasting pattern from a display onto thesurface of the panel; providing a camera paired with the display,wherein the display and camera pair are mounted in a spaced-apartrelationship a known distance and angle from the surface of the panelfor detecting the reflected image of the pattern projected on thesurface of the panel from the display, and wherein the pattern detectedby the camera covers the entire portion of interest on the surface inthe direction of the second dimension of the panel; controlling thecamera to acquire at least one image of the reflected pattern on thepanel as the panel is conveyed across the path of the projected patternin the first direction; analyzing and combining the data acquired by thecamera to construct surface data representative of the surface of thepanel, including at least the steps of developing, for each pixel in inthe viewing area of the camera for each acquired image, a mapping vectorthat defines where the reflected ray projects from the camera origin tothe associated display, and developing, for each pixel in the viewingarea of the camera for each acquired image, the elevation value, s, ofthe point, by simultaneously solving (1) the geometric optical equationand (2) the differential geometry equation, using the mapping vector;and analyzing the data representative of the surface of the panel todetermine optical characteristics of the panel.